One commercial process for the manufacture of 1,1,2-trifluoro-2-chloroethyl methyl ether is a two-step process, as follows: ##STR1##
The first step in this process is expensive because it involves the preparation of the gas CF.sub.2 .dbd.CFCl, which must be distilled under pressure or at low temperature. The solvent methanol must be recovered from the by-product zinc chloride, and disposal of the zinc chloride is a problem.
The second step of this synthesis is efficient, but requires a separate reactor and purification system.
The reaction of certain perhalogenated alkanes with a primary or secondary alkanol and an inorganic base to produce certain halogenated ethers is described in Corley et al, JACS 78, on p. 3491, bottom of col. 1, as follows: EQU CF.sub.2 ClCFCl.sub.2 +KOH+CH.sub.3 OH.fwdarw.CH.sub.3 OCF.sub.2 CHFCl
The text of this article indicates a reaction at 125.degree. for 20 hours, and then:
"The product was taken up in diethyl ether, washed with water, dried and fractionated through a 30-plate column to give a 30% yield (range 20-36%) of CH.sub.3 OCF.sub.2 CHFCl . . . " PA1 "Alkyl ethers containing fluorine were previously prepared by Swartz by the action of alcoholic caustic or metallic carbonate on polyfluorohaloethanes. This procedure was later modified by Gowland." PA1 " . . . CH.sub.2 CLCH(CH.sub.3)CH.dbd.CF.sub.2 . . . is the product which would be expected from CH.sub.2 ClCH(CH.sub.3)CH.sub.2 CF.sub.2 Cl, since it has been shown that the point of attack by a base on molecule containing fluorine is the hydrogen on a carbon adjacent to a cluster of fluorine atoms on a single atom." PA1 X=Br or Cl PA1 Y=Br or Cl PA1 Z=Br, Cl or F.
The results obtained by Corley, in a reaction without a catalyst, generally showed low yields and conversions, and relatively long reaction times.
An article by Scipioni et al, Ann. Chem. Rome, 1967, 57(7), pgs. 817-824, also discusses the reactivity of various halogenated alkanes with alkanols and inorganic bases to product ethers therefrom.
In Fluorine Chemistry Reviews, by Metille and Burton, p. 354, the authors describe the dehalogenation of CF.sub.3 I to CF.sub.3 H, using KOH in a solvent of high dielectric constant, specifically referred to ethanol. The use of the reaction to dehalogenate CF.sub.3 CF.sub.2 I to CF.sub.3 CF.sub.2 H is also discussed.
The source article referred to by Metille and Burton is Banus et al., J. Chem. Soc. 1951, pp. 60-64. This publication states that it is known that the C-I bond in CF.sub.3 I can undergo homolytic fission but that, apart from decomposition, CF.sub.3 Cl, CF.sub.2 Cl.sub.2 and CHF.sub.2 Cl "do not show reactions involving the homolytic or heterolytic fission of the carbon-chloride bond". The publication in general stresses that the iodo compounds are unique as compared to the corresponding bromo or chloro compounds. It would not, therefore, suggest the use of the same type of reaction even for brominated, chlorinated, or fluorinated alkanes, let alone ethers.
Dittman, 2,636,908 relates to dehydrochlorination in the presence of caustic or KOH, to produce CF.sub.2 .dbd.CClF. Alcohol was not used. Other references to dehydrohalogenation may be found in Frederick, U.S. Pat. No. 2,709,181; Young, U.S. Pat. No. 3,391,204, Ex. 15; Miller, U.S. Pat. Nos. 2,803,665 and 2,803,666; Tarrant et al, JACS 76, 2343 at 2344 (1954) and Corley et al, supra at 3489 (1956).
One addition of an alcohol to an olefinically unsaturated perhaloethylene is described in Corley et al, supra, 78 JACS at 3491, where the following reaction is described: EQU CF.sub.2 .dbd.CFCl+KOH+CH.sub.3 OH.fwdarw.CH.sub.3 OCF.sub.2 CHFCl
Park et al, in JACS 70, 1550 (1948), describe the addition of methanol and ethanol to CF.sub.2 .dbd.CFCl. Hanford, U.S. Pat. No. 2,409,274 describes an addition reaction of an unsaturated substrate with an alcohol in the presence of a base, to produce an ether, as follows: EQU CF.sub.2 .dbd.CF.sub.2 +NaOEt+EtOH.fwdarw.CF.sub.2 HCF.sub.2 OC.sub.2 H.sub.5
Another description of a similar alcohol addition reaction appears in Aliphatic Fluorine Compounds, Lovelace et al., Reinhold, 1958, pp. 155-159.
The Lovelace et al text, supra, describes the reaction between fluorocarbon halides and alcoholates as generally producing ethers, citing several examples. The Tarrant and Young work, JACS 75, 932 (1953), is relied upon by Lovelace et al as establishing that the general reaction is not a simple Williamson synthesis.
Young, U.S. Pat. No. 3,391,204 describes the reaction between a perhalogenated fluoro-chloro-substituted alkane and TEA (Ex. 11), which may be in the presence of CuCl.sub.2 (Ex. 12; Col. 7, 11, 6-25) and methanol (Col. 6, 1. 74) or other alkanol (Col. 6, 11, 68-69). The alcohol or other solvent is considered to be an inert diluent (Col. 6, 11, 28, et seq.). Generally, the reaction extracts a chlorine and replaces it with a hydrogen, as in Exs. 7, 8, 11 and 12, but the reaction may go one step further with a dehydrohalogenation step occurring (Exs. 7, 8 and 15) with the production of an ethylenically unsaturated product. Young's reactions do not produce ethers.
Park et al report in JACS 70, at 1550, that:
The Gowland reference is to British Pat. No. 523,449, which describes the following reaction: EQU CHCl.sub.2 CF.sub.2 Cl+KOH+ROH.fwdarw.CHCl.sub.2 CF.sub.2 OR+KCl+H.sub.2 O
Gowland's initial reaction is not perhalogenated.
Other reactions are known in which a halogenated alkane is reacted with an alcohol and an inorganic base, to produce a halogenated ether, but the halogenated alkane is not a perhalogenated compound, as in the present invention, and the reaction mechanism is that of dehydrohalogenation, rather than reduction. These include U.S. Pat. No. 3,637,477, granted Jan. 25, 1972, to L. S. Croix, and assigned to Air Reduction Co., Inc.; and J. Gen. Chem. (U.S.S.R.), 29, 1113-1117 (1959), Soborovskii and Baina, Difluorochloromethane as a Difluoromethylating Agent.
The presence of hydrogen substituents in the halogenated alkane, and its chain length, also affect the reaction. Thus, Tarrant et al, JACS 76, at p. 2344, state:
with a citation to Tarrant and Young, JACS 75, 932 (1953).
U.S. Pat. No. 3,931,238 to Starks discloses the preparation of various alcohols and ethers from halogenated hydrocarbons. In particular, this patentee employs various betaines as catalysts in connection with aqueous alkali metal hydroxide solutions. This patentee does not employ any primary or secondary alkanol reactants, however, and among the betaines includes certain quaternary ammonium salts. No primary, secondary or tertiary amines are said to be useful as catalysts therein. As a matter of fact, this patentee specifically shows in Example 1 that one tertiary amine is comparatively highly inferior to his betaines and excluded from his invention.
Finally, U.S. Pat. No. 2,332,467 to Linn et al relates to the production of mixed ethers by contacting an alcohol with an alkyl halide and zinc at elevated temperatures.